Structure learning of graphical models for task-oriented robot grasping

In the collective imaginaries a robot is a human like machine as any androids in science fiction. However the type of robots that you will encounter most frequently are machinery that do work that is too dangerous, boring or onerous. Most of the robots in the world are of this type. They can be found in auto, medical, manufacturing and space industries. Therefore a robot is a system that contains sensors, control systems, manipulators, power supplies and software all working together to perform a task. The development and use of such a system is an active area of research and one of the main problems is the development of interaction skills with the surrounding environment, which include the ability to grasp objects. To perform this task the robot needs to sense the environment and acquire the object informations, physical attributes that may influence a grasp. Humans can solve this grasping problem easily due to their past experiences, that is why many researchers are approaching it from a machine learning perspective finding grasp of an object using information of already known objects. But humans can select the best grasp amongst a vast repertoire not only considering the physical attributes of the object to grasp but even to obtain a certain effect. This is why in our case the study in the area of robot manipulation is focused on grasping and integrating symbolic tasks with data gained through sensors. The learning model is based on Bayesian Network to encode the statistical dependencies between the data collected by the sensors and the symbolic task. This data representation has several advantages. It allows to take into account the uncertainty of the real world, allowing to deal with sensor noise, encodes notion of causality and provides an unified network for learning. Since the network is actually implemented and based on the human expert knowledge, it is very interesting to implement an automated method to learn the structure as in the future more tasks and object features can be introduced and a complex network design based only on human expert knowledge can become unreliable. Since structure learning algorithms presents some weaknesses, the goal of this thesis is to analyze real data used in the network modeled by the human expert, implement a feasible structure learning approach and compare the results with the network designed by the expert in order to possibly enhance it.

Monte Carlo Simulations of Novel Scintillator Detectors and Dosimetry Calculations

Monte Carlo (MC) simulation techniques are becoming very common in the Medical Physicists community. MC can be used for modeling Single Photon Emission Computed Tomography (SPECT) and for dosimetry calculations. 188Re, is a promising candidate for radiotherapeutic production and understanding the mechanisms of the radioresponse of tumor cells "in vitro" is of crucial importance as a first step before "in vivo" studies. The dosimetry of 188Re, used to target different lines of cancer cells, has been evaluated by the MC code GEANT4. The simulations estimate the average energy deposition/per event in the biological samples. The development of prototypes for medical imaging, based on LaBr3:Ce scintillation crystals coupled with a position sensitive photomultiplier, have been studied using GEANT4 simulations. Having tested, in the simulation, surface treatments different from the one applied to the crystal used in our experimental measurements, we found out that the Energy Resolution (ER) and the Spatial Resolution (SR) could be improved, in principle, by machining in a different way the lateral surfaces of the crystal. We have then studied a system able to acquire both echographic and scintigraphic images to let the medical operator obtain the complete anatomic and functional information for tumor diagnosis. The scintigraphic part of the detector is simulated by GEANT4 and first attempts to reconstruct tomographic images have been made using as method of reconstruction a back-projection standard algorithm. The proposed camera is based on slant collimators and LaBr3:Ce crystals. Within the Field of View (FOV) of the camera, it possible to distinguish point sources located in air at a distance of about 2 cm from each other. In particular conditions of uptake, tumor depth and dimension, the preliminary results show that the Signal to Noise Ratio (SNR) values obtained are higher than the standard detection limit.

Microwave-Mediated Hetero Diels-Alder reaction: Synthesis of biologically active compounds

Heterocyclic compounds represent almost two-thirds of all the known organic compounds: they are widely distributed in nature and play a key role in a huge number of biologically important molecules including some of the most significant for human beings. A powerful tool for the synthesis of such compounds is the hetero Diels-Alder reaction (HDA), that involve a [4+2] cycloaddition reaction between heterodienes and suitable dienophiles. Among heterodienes to be used in such six-membered heterocyclic construction strategy, 3-trialkylsilyloxy-2-aza-1,3-dienes (Fig 1) has been demonstrated particularly attractive. In this thesis work, HDA reactions between 2-azadienes and carbonylic and/or olefinic dienophiles, are described. Moreover, substitution of conventional heating by the corresponding dielectric heating as been explored in the frame of Microwave-Assisted-Organic-Synthesis (MAOS) which constitutes an up-to-grade research field of great interest both from an academic and industrial point of view. Reaction of the azadiene 1 (Fig 1) will be described using as dienophiles carbonyl compounds as aldehyde and ketones. The six-membered adducts thus obtained (Scheme 1) have been elaborated to biologically active compounds like 1,3-aminols which constitutes the scaffold for a wide range of drugs (Prozac®, Duloxetine, Venlafaxine) with large applications in the treatment of severe diseases of nervous central system (NCS). Scheme 1 The reaction provides the formation of three new stereogenic centres (C-2; C-5; C-6). The diastereoselective outcome of these reactions has been deeply investigated by the use of various combination of achiral and chiral azadienes and aliphatic, aromatic or heteroaromatic aldehydes. The same approach, basically, has been used in the synthesis of piperidin-2-one scaffold substituting the carbonyl dienophile with an electron poor olefin. Scheme 2 As a matter of fact, this scaffold is present in a very large number of natural substances and, more interesting, is a required scaffold for an huge variety of biologically active compounds. Activated olefins bearing one or two sulfone groups, were choose as dienophiles both for the intrinsic characteristic flexibility of the “sulfone group” which may be easily removed or elaborated to more complex decorations of the heterocyclic ring, and for the electron poor property of this dienophiles which makes the resulting HDA reaction of the type “normal electron demand”. Synthesis of natural compounds like racemic (±)-Anabasine (alkaloid of Tobacco’s leaves) and (R)- and (S)-Conhydrine (alkaloid of Conium Maculatum’s seeds and leaves) and its congeners, are described (Fig 2).

Mechanosensitivity in the myenteric plexus of the guinea pig ileum

The enteric nervous system regulates autonomously from the central nervous system all the reflex pathways that control blood flow, motility, water and electrolyte transport and acid secretion. The ability of the gut to function in isolation is one of the most intriguing phenomenons in neurogastroenterology. This requires coding of sensory stimuli by cells in the gut wall. Enteric neurons are prominent candidates to relay mechanosensitivity. Surprisingly, the identity of mechanosensitive neurons in the enteric nervous system as well as the appropriate stimulus modality is unknown despite the evidence that enteric neurons respond to sustained distension. Objectives: The aim of our study was to record from mechanosensitive neurons using physiological stimulus modalities. Identification of sensory neurons is of central importance to understand sensory transmission under normal conditions and in gut diseases associated with sensorimotor dysfunctions, such as Irritable Bowel Syndrome. Only then it will be possible to identify novel targets that help to normalise sensory functions. Methods: We used guinea-pig ileum myenteric plexus preparations and recorded responses of all neurons in a given ganglion with a fast neuroimaging technique based on voltage sensitive dyes. To evoke a mechanical response we used two different kinds of stimuli: firstly we applied a local mechanical distortion of the ganglion surface with von Frey hair. Secondarily we mimic the ganglia deformation during physiological movements of myenteric ganglia in a freely contracting ileal preparation. We were able to reliably and reproducibly mimic this distortion by intraganglionic injections of small volumes of oxygenated and buffered Krebs solution using stimulus parameters that correspond to single contractions. We also performed in every ganglion tested, electrical stimulations to evoke fast excitatory postsynaptic potentials. Immunohistochemistry reactions were done with antibodies against Calbindin and NeuN, considered markers for sensory neurons. Results: Recordings were performed in 46 ganglia from 31 guinea pigs. In every ganglion tested we found from 1 to 21 (from 3% to 62%) responding cells with a median value of 7 (24% of the total number of neurons). The response consisted of an almost instantaneous spike discharge that showed adaptation. The median value of the action potential frequency in the responding neurons was 2.0 Hz, with a recording time of 1255 ms. The spike discharge lasted for 302 ± 231 ms and occurred only during the initial deformation phase. During sustained deformation no spike discharge was observed. The response was reproducible and was a direct activation of the enteric neurons since it remained after synaptic blockade with hexamethonium or ω-conotoxin and after long time perfusion with capsaicin. Muscle tone appears not to be required for activation of mechanosensory neurons. Mechanosensory neurons showed a response to mechanical stimulation related to the stimulus strength. All mechanosensory neurons received fast synaptic inputs. There was no correlation between mechanosensitivity and Calbindin-IR and NeuN-IR (44% of mechanosensitive neurones Calb-IR-/NeuN-IR-). Conclusions: We identified mechanosensitive neurons in the myenteric plexus of the guinea pig ileum which responded to brief deformation. These cells appear to be rapidly accommodating neurons which respond to dynamic change. All mechanosensitive neurons received fast synaptic input suggesting that their activity can be highly modulated by other neurons and hence there is a low stimulus fidelity which allows adjusting the gain in a sensory network. Mechanosensitivity appears to be a common feature of many enteric neurons belonging to different functional classes. This supports the existence of multifunctional enteric neurons which may fulfil sensory, integrative and motor functions.

Transgenic mice as a tool for depression research: examples from the endocannabinoid and the corticotropin-releasing hormone system

Major depression belongs to the most serious and widespread psychiatric disorders in today’s society. There is a great need for the delineation of the underlying molecular mechanisms as well as for the identification of novel targets for its treatment. In this thesis, transgenic mice of the endocannabinoid and the corticotropin-releasing hormone (CRH) system were investigated to determine the putative role of these systems for depression-like phenotypes in mice. In the first part of the thesis, we found that the endocannabinoid system was prominently involved in a brain region-specific and temporally controlled manner in acute as well as in chronic stress processing. Genetic deletion in combination with pharmacological intervention revealed the importance of a fully functional endocannabinoid system for efficient neuroendocrine and behavioral stress coping. Accordingly, cannabinoid type 1 (CB1) receptor-deficient mice displayed several depression-like symptoms and molecular alterations, including “behavioral despair”, stress hormone hypersecretion and decreased glucocorticoid receptor and brain-derived neurotrophic factor expression in the hippocampus. However, the endocannabinoid system was dispensable for the efficacy of currently used antidepressant drugs. To facilitate future endocannabinoid research, a transgenic mouse was generated, which overexpressed the CB1 receptor protein fused to a fluorescent protein. In the second part of the thesis, conditional brain region-specific CRH overexpressing mice were evaluated as a model for pathological chronic CRH hyperactivation. Mutant mice showed aberrant neuroendocrine and behavioral stress coping and hyperarousal due to CRH-induced activation of the noradrenergic system in the brain. Mutant mice appeared to share similarities with naturally occurring endogenous CRH activation in wild-type mice and were sensitive to acute pharmacological blockade of CRH receptor type 1 (CRH-R1). Thus, CRH overexpressing mice serve as an ideal in vivo tool to evaluate the efficacy of novel CRH-R1 antagonists. Together, these findings highlight the potential of transgenic mice for the understanding of certain endo-phenotypes (isolated symptoms) of depression and their molecular correlates.

Exact computation of the adjacency graph of an arrangement of quadrics

Präsentiert wird ein vollständiger, exakter und effizienter Algorithmus zur Berechnung des Nachbarschaftsgraphen eines Arrangements von Quadriken (Algebraische Flächen vom Grad 2). Dies ist ein wichtiger Schritt auf dem Weg zur Berechnung des vollen 3D Arrangements. Dabei greifen wir auf eine bereits existierende Implementierung zur Berechnung der exakten Parametrisierung der Schnittkurve von zwei Quadriken zurück. Somit ist es möglich, die exakten Parameterwerte der Schnittpunkte zu bestimmen, diese entlang der Kurven zu sortieren und den Nachbarschaftsgraphen zu berechnen. Wir bezeichnen unsere Implementierung als vollständig, da sie auch die Behandlung aller Sonderfälle wie singulärer oder tangentialer Schnittpunkte einschließt. Sie ist exakt, da immer das mathematisch korrekte Ergebnis berechnet wird. Und schließlich bezeichnen wir unsere Implementierung als effizient, da sie im Vergleich mit dem einzigen bisher implementierten Ansatz gut abschneidet. Implementiert wurde unser Ansatz im Rahmen des Projektes EXACUS. Das zentrale Ziel von EXACUS ist es, einen Prototypen eines zuverlässigen und leistungsfähigen CAD Geometriekerns zu entwickeln. Obwohl wir das Design unserer Bibliothek als prototypisch bezeichnen, legen wir dennoch größten Wert auf Vollständigkeit, Exaktheit, Effizienz, Dokumentation und Wiederverwendbarkeit. Über den eigentlich Beitrag zu EXACUS hinaus, hatte der hier vorgestellte Ansatz durch seine besonderen Anforderungen auch wesentlichen Einfluss auf grundlegende Teile von EXACUS. Im Besonderen hat diese Arbeit zur generischen Unterstützung der Zahlentypen und der Verwendung modularer Methoden innerhalb von EXACUS beigetragen. Im Rahmen der derzeitigen Integration von EXACUS in CGAL wurden diese Teile bereits erfolgreich in ausgereifte CGAL Pakete weiterentwickelt.

An angiographic analysis of atherosclerosis progression in below-the-knee arteries after femoropopliteal angioplasty in claudicants

Purpose: To report an angiographic investigation of midterm atherosclerotic disease progression in below-the-knee (BTK) arteries of claudicants. Methods: Angiograms were performed in 58 consecutive claudicants (35 men; mean age 68.3±8.7 years) with endovascular treatment of femoropopliteal arteries in 58 limbs after a mean follow-up of 3.6±1.2 years. Angiograms were reviewed in consensus by 2 experienced readers blinded to clinical data. Progression of atherosclerosis in 4 BTK arterial segments (tibioperoneal trunk, anterior and posterior tibial arteries, and peroneal artery) was assessed according to the Bollinger score. The composite per calf Bollinger score represented the average of the 4 BTK arterial segment scores. The association of the Bollinger score with cardiovascular risk factors and gender was scrutinized. Results: A statistically significant increase in atherosclerotic burden was observed for the mean composite per calf Bollinger score (5.7±8.3 increase, 95% CI 3.5 to 7.9, p<0.0001), as well as for each single arterial segment analyzed. In multivariate linear regression analysis, diabetes mellitus was associated with a more pronounced progression of atherosclerotic burden in crural arteries (β: 5.6, p=0.035, 95% CI 0.398 to 10.806). Conclusion: Progression of infrapopliteal atherosclerotic lesions is common in claudicants during midterm follow-up. Presence of diabetes mellitus was confirmed as a major risk factor for more pronounced atherosclerotic BTK disease progression.

Endovascular treatment of a traumatic direct carotid-cavernous fistula using the Amplatzer Vascular Plug II

To report the use of the second-generation Amplatzer Vascular Plug II (AVP II) for the treatment of a posttraumatic type A carotid-cavernous fistula (CCF).

Sphingosine kinase 1 is critically involved in nitric oxide-mediated human endothelial cell migration and tube formation

Sphingosine kinases (SKs) convert sphingosine to sphingosine 1-phosphate (S1P), which is a bioactive lipid that regulates a variety of cellular processes including proliferation, differentiation and migration.

Reduced trabecular bone mineral density and cortical thickness accompanied by increased outer bone circumference in metacarpal bone of rheumatoid arthritis patients: a cross-sectional study

Introduction The objective of this study was to assess three-dimensional bone geometry and density at the epiphysis and shaft of the third meta-carpal bone of rheumatoid arthritis (RA) patients in comparison to healthy controls with the novel method of peripheral quantitative computed tomography (pQCT). Methods PQCT scans were performed in 50 female RA patients and 100 healthy female controls at the distal epiphyses and shafts of the third metacarpal bone, the radius and the tibia. Reproducibility was determined by coefficient of varia-tion. Bone densitometric and geometric parameters were compared between the two groups and correlated to disease characteristics. Results Reproducibility of different pQCT parameters was between 0.7% and 2.5%. RA patients had 12% to 19% lower trabecular bone mineral density (BMD) (P ≤ 0.001) at the distal epiphyses of radius, tibia and metacarpal bone. At the shafts of these bones RA patients had 7% to 16% thinner cortices (P ≤ 0.03). Total cross-sectional area (CSA) at the metacarpal bone shaft of pa-tients was larger (between 5% and 7%, P < 0.02), and relative cortical area was reduced by 13%. Erosiveness by Ratingen score correlated negatively with tra-becular and total BMD at the epiphyses and shaft cortical thickness of all measured bones (P < 0.04). Conclusions Reduced trabecular BMD and thinner cortices at peripheral bones, and a greater bone shaft diameter at the metacarpal bone suggest RA spe-cific bone alterations. The proposed pQCT protocol is reliable and allows measuring juxta-articular trabecular BMD and shaft geometry at the metacarpal bone.

Computational biomechanics to simulate the femoropopliteal intersection during knee flexion: a preliminary study

To assess if finite element (FE) models can be used to predict deformation of the femoropopliteal segment during knee flexion.

Endovascular treatment of patients with types A and B thoracic aortic dissection using Relay thoracic stent-grafts: results from the RESTORE Patient Registry

To evaluate the safety and performance of Relay stent-grafts in patients with acute or chronic aortic dissections.